Previous quantum photonics experiments required the use of “bulk optics.” These space-consuming elements would be distributed across the optical table and could occupy vast amounts of laboratory space. Now, p
hotonic chips are changing this landscape, including for quantum photonics. Monolithic integration of single-photon sources, in a controllable way, would give a resource-efficient route to implement millions of photonic qubits in PICs. To run quantum computation protocols, these photons must be indistinguishable. With this, industrial-scale photonic quantum processor production would become feasible.However, the currently established fabrication method stands in the way of the compatibility of this promising concept with current semiconductor technology.
In a first attempt, which was detailed in work published about two years ago, the researchers generated single photons on a silicon wafer, but only in a random, nonscalable way.
“Now, we show how focused ion beams from liquid metal alloy ion sources are used to place single-photon emitters at desired positions on the wafer while obtaining a high creation yield and high spectral quality,” said Nico Klingner, a physicist at HZDR.
Furthermore, the researchers subjected the same single-photon emitters to a rigorous material testing program. After several cooling-down and warming-up cycles, they did not observe any degradation of their optical properties. These findings meet the preconditions required for mass production.
To translate this achievement into a widespread technology and allow for wafer-scale engineering of individual photon emitters on the atomic scale compatible with established foundry manufacturing, the researchers attained broad-beam implantation in a commercial implanter through a lithographically defined mask. According to Ciarán Fowley, cleanroom group leader and head of nanofabrication and analysis at HZDR, the development allowed the researchers to use both the silicon-processing cleanroom as well as electron beam lithography machines.
Using both methods, the researchers reported that they can create dozens of telecom single-photon emitters at predefined locations with a spatial accuracy of about 50 nm. The units emit in the O-band and exhibit stable operation over days under continuous-wave excitation.
These single-photon emitters are now technologically ready for production in semiconductor fabs and incorporation into the existing telecommunication infrastructure, the researchers said.
The research was published in Nature Communications (www.doi.org/10.1038/s41467-022-35051-5).
